Thermal management presents a substantial engineering challenge at both small and large scales, and across many contexts. For example, a person outdoors will typically be exposed to a constantly changing range of ambient temperatures depending on solar radiation, air temperature, cloud cover, wind, and other factors that can cause dramatic temperature swings over short time scales. Additionally, the person's level of physical activity will change over short time scales depending on their level of activity (e.g. sedentary vs. walking vs. strenuous work or exercise) and this will have a large impact on the person's thermal status. Thermal management is an issue at larger scales as well, for example in heat management of buildings and other structures, where excess heat often needs to be removed in order to keep the interior of the building comfortable or interior heat needs to be retained against loss to the environment to keep the building sufficiently warm.
Thermal management can be aided by the use of infrared reflecting coatings known in the art, including gold, aluminum, polyvinylidene fluoride, and fibrous clays. However, such coatings have various shortcomings such as expense, toxic manufacturing processes, and limited compatibility with textiles and other soft substrates. More fundamentally, the prior art IR coatings are not dynamic and their IR reflectance cannot be tuned to respond to constantly changing thermal conditions.
Accordingly, there is a need in the art for novel IR coatings that reflect substantial amounts of IR radiation. There is also a need in the art for IR coatings that can be applied to soft materials such as fibers and textiles. There is also a need in the art for non-toxic IR coatings derived from natural sources. And there is a completely unmet need in the art for dynamic IR coatings having a tunable IR reflectance. These and other needs are met by the inventions disclosed herein.